The magnetotelluric (MT) method, a technique for probing the electrical conductivity structure of the Earth, is increasingly used both in applied geophysics and in basic research. This book, first published in 2005, goes into detail on practical aspects of applying the MT technique. Beginning with the basic principles of electromagnetic induction in the Earth, this introduction to magnetotellurics aims to guide students and researchers in geophysics and other areas of Earth science through the practical aspects of the MT method: from planning a field campaign, through data processing and modelling, to tectonic and geodynamic interpretation. The book will be of use to graduate-level students and researchers who are embarking on a research project involving MT; to lecturers preparing courses on MT; and to geoscientists involved in multi-disciplinary research projects who wish to incorporate MT results in their interpretations.